CVD reactor with substrate holder which is rotatably driven and mounted by a gas stream

ABSTRACT

The invention relates to a device for depositing layers, particularly crystalline layers, onto substrates. Said device comprises a process chamber arranged in a reactor housing where the floor thereof, comprises at least one substrate holder which is rotatably driven by a gas flow flowing in a feed pipe associated with said floor. Said substrate holder is disposed in a bearing cavity on a gas cushion and held in place thereby. The aim of the invention is to technologically improve the design of a substrate holder which is rotatably mounted in a gas flow, particularly in a linear cross-flowing process chamber. Said bearing cavity is associated with a tray-shaped element arranged below the outflow of the feed pipe.

[0001] This application is a continuation of pending InternationalPatent Application No. PCT/EP01/12311 filed Oct. 25, 2001, whichdesignates the United States and claims priority of pending GermanApplication No. 100 55 182.3, filed Nov. 8, 2000.

FIELD OF THE INVENTION

[0002] The invention relates to a device for depositing in particularcrystalline layers on in particular crystalline substrates, having aprocess chamber which is disposed in a reactor housing and the base ofwhich carries at least one substrate holder, which is carried on a gascushion in a bearing recess and is driven in rotation by the gas streamwhich maintains the gas cushion and flows through a feed line associatedwith the base.

[0003] Devices of this type are used, for example, to depositsemiconductor layers from the vapor phase by means of reaction gases fedto the substrate. At least the base of the process chamber is heated, sothat the reaction gases decompose in the vapor phase which is heated asa result of the process chamber wall heating, and the decompositionproducts condense on the substrate. WO 96/23913 has disclosed, forexample, a device for the epitaxial growth of silicon carbide, in whichthe process chamber is formed by a graphite tube which is heated usinghigh frequency. It is known from this document for the substrate not tobe placed directly onto the process chamber base, but rather onto aplate which rests on the base.

[0004] U.S. Pat. No. 6,039,812 A has likewise already disclosed a CVDreactor for deposition of silicon carbide. In this case, the entry tothe process chamber is connected to a gas inlet system by means of atube.

[0005] U.S. Pat. No. 4,961,399 shows a CVD rector with substrate holderwhich is mounted rotatably on a gas cushion and is driven in rotation bythe gas stream. In this case, the process chamber is disposed as acylinder symmetrically around a gas inlet element. In this case, thereis a total of five rotatable substrate holders.

[0006] The invention is based on the object of technologicallydeveloping the concept of the substrate holder mounted rotatably on agas stream in particular in a linear-flow process chamber.

[0007] The object is achieved by the invention given in the claims.

[0008] Claim 1 provides, firstly and substantially, that the bearingrecess is associated with a tray disposed above the outlet opening ofthe feed line. In the case of a tunnel-like, linear-flow reactor, thistray can be removed on one side, in particular through the downstreamopening in the process chamber, in order to change the substrate on thesubstrate holder. In a preferred development of the invention, there isprovision for the tray to be equipped with an annular bead. This annularbead faces downward. Within the region surrounded by the annular bead itis preferable for there to be passage openings, through which the gaswhich carries the substrate holder and drives it in rotation can flow.This annular bead is preferably located in an annular groove associatedwith a step of the process chamber base. This ensures automaticcentering and holding of the tray in the step of the process chamberbase. The annular bead, which preferably tapers to a sharp edge, bearsagainst the base of the annular groove in such a manner as to form aseal, so that a closed volume is formed between the surface of the stepand the underside of the tray, into which volume the opening of the feedline opens out. This volume is used to distribute the gas of the gasstream flowing through the opening to a multiplicity of passageopenings, which open out, in a known way, in helical grooves in the baseof the bearing recess, in order in this way to bearingly support thesubstrate holder and drive it in rotation. The feed line preferably runsinside a graphite body which forms the base. The feed line preferablybegins below the upstream process chamber opening, so that there are twoopenings disposed above one another, to which gas inlet tubes can beconnected in order to feed the reaction gases into the process chamberand an inert gas from the feed line. These two pipelines run parallel toone another and originate from a common gas inlet member.

[0009] An independent inventive development of the device of the generictype provides that the base is formed by a cavity section of an inparticular multipart graphite tube which has a substantially rectangularinternal cross-sectional profile, a gas inlet element for one or morereaction gases being associated with the first tube end, and the secondtube end forming a loading opening for the process chamber, and areaction-gas inlet tube leading from the gas inlet member to theend-side opening of the process chamber, and a separate tube leadingfrom the gas inlet member to the feed line opening below it.

[0010] The invention also relates to a method for depositing inparticular silicon carbide by means of metal-organic compounds whichhave been converted to the vapor phase. According to the invention, itis provided that a tray is disposed in the process chamber. This tray isremovable in order for the process chamber to be loaded with thesubstrates and for the substrates to be unloaded from the processchamber.

BRIEF DESCRIPTION OF DRAWINGS

[0011] An exemplary embodiment of the invention is explained below withreference to appended drawings, in which:

[0012]FIG. 1 shows a sectional illustration through a CVD reactor,

[0013]FIG. 2 shows an enlarged illustration of the base of the processchamber in the region of its downstream end, and

[0014]FIG. 3 shows a section on section lines III-III in FIGS. 1 and 2.

DETAILED DESCRIPTION OF DRAWINGS

[0015] The exemplary embodiment relates to a CVD reactor for thedeposition of silicon carbide layers, as is fundamentally already knownfrom U.S. Pat. No. 6,039,812 and WO 96/23913. The rector has a reactorhousing 1, which is formed as a quartz tube. Around this quartz tubethere is an HF coil (not shown) for heating the process chamber. Theprocess chamber 2 is located inside the reactor housing and comprises amultipart graphite tube. The graphite tube has a base 3 which is formedby a graphite body 20. The process chamber 2 disposed above the base 2is laterally delimited by two walls 22, on which there is a cover 23.Around the graphite tube 20, 22, 23 there is a graphite foam sleeve 21.At both end sides of the graphite bodies 20, 22, 23 there are disks 24,25 which consist of solid graphite.

[0016] The end opening of the process chamber 2 which is disposed at theupstream end 10 is connected to a gas inlet element 9 by means of areaction gas inlet tube 12. The reaction gases flow through thisreaction gas inlet tube 12 into the process chamber 2.

[0017] Below the reaction gas inlet tube 12 there is a tube 13 throughwhich an inert gas is passed. This tube 13 opens out into an opening ofa feed line 5 which runs in the process chamber base 3. The feed line 5opens out into the base of a downstream step 15 of the process chamberbase 3.

[0018] A tray 8 is disposed on the step 15. The step 15 forms an annulargroove 17 which surrounds the outlet opening 7 of the feed line 5. Anannular bead 14, which belongs to the underside of the tray 8 and tapersto a sharp edge, is supported on the base of the annular groove 17.Together with the annular groove 17, this bead 14 forms a closed volumewhich is a gas-distribution chamber 27. Passage openings 18 lead out ofthis gas distribution chamber 27 into a bearing recess 4 of the tray 8.There, the passage openings 18 open out into helical grooves (not shown)which are formed into the base of the bearing recess 4.

[0019] A substrate holder 6 which is in the form of a circular diskrests in the bearing recess 4. The gas stream which emerges through thepassage opening 8 lifts the substrate holder 6 in a known way. As aresult of the helical orientation of the grooves, the substrate holder 6is not only bearingly supported by the gas stream but also is driven inrotation by it. The substrate to be coated, which is not illustrated, islocated on the substrate holder 6. It may be surrounded by a siliconcarbide ring 26.

[0020] The tray 8 has an extension which projects out of the downstreamend 11 of the process chamber 2. This extension has a tool engagementopening 19, to which a tool can be fitted in order for the tray 8 to beremoved from the process chamber 2. For this purpose, the tray 8 firsthas to be lifted, so that the annular bead 14 moves out of the groove17. Then, the tray 8, together with all the substrate holders 6 locatedon it, can be removed from the process chamber 2.

[0021] The graphite bodies of the process chamber may be coated withsilicon carbide or tantalum carbide.

[0022] The gas flow in the two pipelines 12, 13 is parallel.Accordingly, the reaction gas flow in the process chamber 2 is alsoparallel to the flow of the inert gas in the feed line 5.

[0023] All features disclosed are (inherently) pertinent to theinvention. The disclosure content of the associated/appended prioritydocuments (copy of the prior application) is hereby incorporated in itsentirety in the disclosure of the application, partly with a view toincorporating features of these documents in claims of the presentapplication.

1. Device for depositing in particular crystalline layers on inparticular crystalline substrates, having a process chamber (2) which isdisposed in a reactor housing (1) and the base (3) of which carries atleast one substrate holder (6), which is carried on a gas cushion in abearing recess (4) and is driven in rotation by the gas stream whichmaintains the gas cushion and flows through a feed line (5) associatedwith the base, characterized in that the bearing recess (4) isassociated with a tray (8) disposed above the outlet opening (7) of thefeed line (5).
 2. Device according to one or more of the precedingclaims or in particular according thereto, characterized in that thetray bears, by means of a sealing bead (14), against a step (15) of agraphite body (16) which forms the base (3).
 3. Device according to oneor more of the preceding claims or in particular according thereto,characterized in that the annular sealing bead (14) is located in anannular groove (17) associated with the step (15).
 4. Device accordingto one or more of the preceding claims or in particular accordingthereto, characterized by passage openings (18) which, offset withrespect to the outlet opening (7) surrounded by the annular groove (17),are surrounded by the sealing bead (14), for the bearing-gas stream topass into the bearing recess (4).
 5. Device according to one or more ofthe preceding claims or in particular according thereto, characterizedin that the bearing-gas stream in the feed line (5) flows in the samedirection as the flow of the reaction gases in the process chamber (2).6. Device for depositing in particular crystalline layers on inparticular crystalline substrates, having a process chamber (2) which isdisposed in the reactor housing (1) and the base (3) of which carries atleast one substrate holder (6), which is carried on a gas cushion in abearing recess (4) and is driven in rotation by the gas stream whichmaintains the gas cushion and flows through a feed line (5) associatedwith the base, characterized in that the base (3) is formed by a cavitysection of an in particular multipart graphite tube (20, 22, 23) whichhas a substantially rectangular internal cross-sectional profile, a gasinlet element (9) for one or more reaction gases being associated withthe first tube end (10), and the second tube end (11 ) forming a loadingopening for the process chamber (2), and a reaction-gas inlet tube (12)leading from the gas inlet member (9) to the end-side opening of theprocess chamber (2), and a separate tube (13) leading from the gas inletmember (9) to the feed line opening below it.
 7. Device according to oneor more of the preceding claims or in particular according thereto,characterized in that the graphite tube (20, 22, 23) which forms theprocess chamber (2) is surrounded by a graphite foam sleeve (21). 8.Device according to one or more of the preceding claims or in particularaccording thereto, characterized by graphite disks (24, 25) disposed infront of the end side of the graphite tube (20, 22, 23) and of thegraphite foam sleeve (21).
 9. Method for depositing in particularsilicon carbide by means of metal-organic compounds which have beenconverted to the vapor phase in a process chamber (2) which is disposedin a reactor housing (1) and the base (3) of which carries at least onesubstrate holder which is carried on a gas cushion in a bearing recess(4) and is driven in rotation by the gas stream which maintains the gascushion and flows through a feed line (5) associated with the base, thebearing recess (4) being associated with a tray (8) which is disposedabove the outlet opening (7) of the feed line (5) and is removed inorder for the process chamber to be loaded and unloaded.